It's remedial, but it'll keep you from slamming your head against the desk when your Mac suddenly decides it can't remember the extra RAM you installed in it:

The guys at MacFixIt are reporting that several users are reporting issues in which their Mac Pro computers are failing to recognize the full amount of RAM installed.

One testimonial went as follows:

"I'm having trouble with my RAM upgrade. I just bought a new 2.8 dual quad core MacPro with 2GB of RAM (2x1GB). I bought an additional 4GB RAM (2x2GB) from TransIntl. However, the most my Mac will see is 4GB, no matter how I configure the RAM."

Another user reported a similar issue in which a newly installed two gigabyte RAM chip failed to be recognized.

The article offers the following fixes:

The first thing one should do is ensure the RAM risers and the individual RAM sticks are properly seated, and that the RAM is installed in matched pairs, following Apple's instructions. Firmly press them down into the riser cards and give them a slight wiggle to ensure they're seated all the way down. Be sure you are properly grounded so as not to harm the RAM with static electricity discharges.

Another reliable standby is to reset the Parameter RAM (a.k.a., PRAM) by holding down the option-command-P-R keys all at once during boot and waiting for a second boot chime. After the second chime, release the keys and allow the Mac to boot normally. Performing this task allows RAM-related firmware variables to reset and for the RAM to register properly in many cases.

If you've seen this problem on your end or have found your own fixes for RAM-related problems, let us know over in the comments or forums.